No abstract

The lattice constants of boron carbides have been determined by powder X-ray diffraction for samples with compositions between about 7.7 and 20.5 at.% carbon. The boundaries of the single-phase region are at about 9 at.% carbon and near, but likely somewhat less than, 20 at.% carbon. The composition dependence of the lattice constants thus established provides a method of assessing the carbon concentration of unknown materials. In particular, assignment of the approximate composition of single crystals used in previous studies allows for a systematic examination of changes in interatomic separation as a function of composition. These changes are discussed in terms of a structural model of the boron carbide solid solution.

The electrical conductivities and Seebeck coefficients of boron carbides, B12+xC3-X with 0.06 S x 1.7, have been measured from 8 K to as high as 1750 K. At high temperature, the temperature ,